Hydrocolloids are derived from polysaccharides that can be extracted from the endosperm of seeds from plants, shrubs and trees of the families Leguminosae and Fabraceae. The seeds of the tamarind tree, Tamarindus indica L. (tamarind gum); Greek hay, Trigonella foenum-graecum L. (fenugreek gum); wild senna and sicklepod plants, Cassia tora and Cassia obtusifolia (cassia gum); the carob tree Ceratonia siliqua L. (locust bean gum); the tara bush Caesalpinia spinosa L. (tara gum), and the guar plant Cyamopsis tetragonoloba L. (guar gum) are common sources for endosperm material. The polysaccharides obtained from these seeds are known to act as thickening and gelling agents in aqueous systems. The polysaccharides obtained from fenugreek gum, cassia gum, locust bean gum, tara gum, and guar gum are known as polygalactomannans. A polygalactomannan is composed of 1→4-linked β-D-mannopyranosyl units with recurring 1→6-linked α-D-galactosyl side groups branching from the number 6 carbon of a mannopyranose residue in the backbone. The galactomannan polymers of the different species of the Leguminosae and Fabraceae families defer from one another in the frequency of the occurrence of the galactosyl side units branching from the polymannopyranose backbone. The average ratio of D-mannosyl to D-galactosyl units in the polygalactomannan contained in fenugreek gum is approximately 1:1, in guar gum approximately 2:1, for tara gum approximately 3:1, for locust bean gum approximately 4:1, and approximately 5:1 for cassia gum. For illustrative purposes, the polygalactomannan obtained from cassia gum is schematically represented in the structure below.
wherein n represents the number of repeating units in the galactomannan polymer. In one embodiment, n represents an integer from about 10 to about 50. In another embodiment, n represents and integer from about 15 to about 35, and in still another embodiment from about 20 to about 30. In still another embodiment of the invention, the polygalactomannan of the invention has a number average molecular weight of at least 100,000. In another embodiment, the number average molecular weight ranges from about from about 150,000 to about 500,000, and in still another embodiment from about 200,000 to about 300,000 (molecular weights determined by GPC method using a polystyrene standard). In a further embodiment of the invention, the number average molecular weight can range from 500,000 to over 1,000,000.
Typically, the endosperm flour extracted from the seeds of cassia, locust bean, tara and guar contains 3 to 12% water, up to 2% fat, up to 7% raw protein, up to 4% raw fiber, up to 2% ash, and at least 75% residual polysaccharide. It has always been a desire to prepare a purer galactomannan with improved its properties to broaden the spectrum of its use such as, for instance, for use in food products for human and animal consumption, as well as in personal care, pharmaceutical, homecare, and industrial compositions. For example, in prior processes, cassia flour was extracted from the seeds of Cassia tora or from Cassia obtusifolia by heating the ripe seeds followed by subjecting them to mechanical stress such as crushing or grinding. This treatment resulted in the pulverization of the germ and the endosperm hull. The intact seed endosperm was isolated from the seedling and hull fragments by sifting and then was subjected to a pulverization process such as described in. U.S. Pat. No. 2,891,050. Although the cassia endosperm flour isolated in this way had the desired gelling properties, it nonetheless retained a specific fruity aroma and a slightly bitter taste. Moreover, the flour had a yellow to slight-brown color so that its use in the production of products requiring high clarity was limited.
In German published patent application DE 3335593, gelling and thickening agents based on a mixture of cassia galactomannans and carrageenan, agar and/or xanthan are disclosed.
German published patent application DE 3347469 describes substituted alkyl ethers of the polysaccharides that appear in the endosperm of cassia tora and their use as a thickening agent in printing pastes for textile printing.
German published patent application DE 3114783 discloses the production of carob pod, carob kernel or guar flour with an improved taste. In the disclosed process, the dried (and where applicable, toasted and ground) base material is subjected to high-pressure extraction with supercritical carbon dioxide. However, the application of this process to cassia flour yields inadequate results.
Heretofor, it has not been possible either through selective pulverization and other mechanical purification processes to successfully produce galactomannan flour such as cassia flour which is substantially colorless, odorless and tasteless and which is largely free of anthraquinones while maintaining gelling properties. For this reason, the cassia flour produced by the prior methods is unsuitable as an additive for high purity, sensorily sophisticated food products.
U.S. Pat. No. 4,840,811 discloses a process for producing cassia endosperm flour from the endosperm of Cassia tora. The obtained product is colorless, odorless and tasteless. In the disclosed method, the endosperm is solvent extracted at least once to reduce impurities such as derivatives of anthraquinones. The extraction solvent comprises a mixture of water and an alkanol and/or acetone. Following drying, the endosperm is converted to a desired degree of fineness.
Independent from the fact that the gelling agent should provide food products with a gelatinous consistency while not affecting the product in terms of taste, odor and color properties, it has been found that the final hydrocolloid resulting from prior art processes still contains certain phytochemicals, in particular, derivatives of anthraquinones. This class of compounds has been identified as potentially hazardous to human health (S. O. Mueller, et al., “Food and Chemical Toxicology” 37 (1999), pages 481 to 491).
Typical anthraquinone derivatives suspected of causing undesirable health effects are 1,8-hydroxy anthraquinones such as physcion, chrysophanol, aloe-emodin and rhein as represented by the following formula:

As discussed above, U.S. Pat. No. 4,840,811 is directed to a method for reducing the level of anthraquinones in cassia gums because of anthraquinones deleteriously affect odor, taste and color. The '811 disclosure does not recognize the toxicity problem inherent in the presence of anthraquinones in the gum. However, in order to provide a cassia hydrocolloid which can be safely used for food, fodder, pharmaceutical and personal care purposes, it is imperative that the hydrocolloid it is substantially free of potentially hazardous anthraquinones.
U.S. Pat. No. 5,801,116 discloses a process for the treatment of guar splits with water to hydrate the splits and then grinding the hydrated split in a laboratory grinder. The ground split is then dried in a bed drier.
V. P. Kapoor, et al. (Carbohydrate Research, 306 (1998), pages 231 to 241) discloses separating endosperm from the seeds of Cassia spectabilis by dry and wet milling processes using various mixers, sieves and grinders. The crude gum, isolated through the dry/wet milling process is subsequently purified by dispersing the gum in water and precipitating the product with ethanol.
U.S. Pat. No. 2,891,050 discloses a process for the production of mucilaginous material from leguminous seeds such as guar, tara and locust bean comprising the steps of tempering the endosperm obtained to a moisture content of 30 to 60% water and flattening the moisturized endosperm by passing it between rollers. In a subsequent step the flattened endosperm is dried and ground. This process is known In the art as the “flaking/grinding” process. The galactomannans prepared according to this process are used as additives in the manufacture of paper, salad dressing, ice cream, bakery products and other foodstuffs.
German published patent application DE 10047278 discloses that endosperm flour of Cassia seeds can be obtained by subjecting the seeds to simple milling processes to separate the endosperm from the husks, followed by grinding the endosperm to yield a desired particle size. It is further disclosed that blending the ground endosperm of Cassia obtusifolia/tora with other hydrocolloids such as carrageenan, xanthan, agar or polyacrylates results in improved gelling and thickening properties.